A type of disc brake system wherein a caliper assembly, which is designed to urge a pair of braking pad assemblies towards each side of disc rotor, is operated by a slide pin device mounted on a torque receiving member fixed to a stationary member and a guide hole bored in the caliper is well-known. In this type of disc brake system, the slide pin device is usually constructed such that a bolt is pierced through a sleeve and then threaded into, at one end portion thereof, a torque receiving member. In such a case, there is a tendency, when the bolt is screwed in or turned back, for the sleeve to rotate together with the bolt. The accompanying rotation of the sleeve with the bolt may cause the dust-boots disposed between the sleeve and the caliper or the torque receiving member to be twisted and sometimes damaged thereby allowing dust to adhere to the external sleeve and preventing smooth operation of the caliper mechanism.
For this reason, the sleeves have been conventionally manufactured with a flange, etc., on one end on the side of the bolt head, having a larger diameter than in the rest part thereof, for being engaged with a different tool from that for screwing up or turning back the bolt, so as to prevent the sleeve when the bolt is screwed forward or rearward from being rotated with the bolt. The way of manufacturing and the material for manufacturing the sleeve must be consequently subjected to some limited conditions, resulting, of course, in a rise in production cost.